Proxy schemes for voice-over-LTE calls

ABSTRACT

A method includes, in a wireless data network, monitoring communication conditions at an intermediate location between a wireless communication terminal and a network element that provides voice-call services over the network to the wireless communication terminal. Upon detecting that the communication conditions are expected to cause the wireless communication terminal to send a notification to the network element, an early notification is sent to the network element on behalf of the terminal. Another method includes detecting a notification in which a terminal notifies a network element of degraded reception performance. A modification, which the network element is expected to perform in a transmission characteristic to the terminal in response to the notification, is predicted. In-flight communication traffic, which is en-route to the terminal and whose transmission characteristic is not yet modified in response to the notification, is intercepted. The predicted modification is applied to the in-flight communication traffic.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication 62/012,999, U.S. Provisional Patent Application 62/013,000and U.S. Provisional Patent Application 62/013,002, all filed Jun. 17,2014, whose disclosures are incorporated herein by reference. Thisapplication is related to a U.S. patent application Ser. No. 14/738,957entitled “Efficient processing of Voice-over-LTE call setup,” filed oneven date, whose disclosure is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates generally to wireless communication, andparticularly to methods and systems for enhancing performance of voicecalls exchanged over data networks.

BACKGROUND OF THE INVENTION

Evolved UMTS Terrestrial Radio Access (E-UTRA) protocol, also referredto as Long-Term Evolution (LTE), is a wireless communication protocolspecified by the Third Generation Partnership Project (3GPP). Advancedversions of the LTE are referred to as LTE-Advanced (LTE-A). As part ofthe IP Multimedia Subsystem (IMS) architecture used in LTE and LTE-A,several protocols have been developed for transferring voice calls overLTE networks. These protocols are referred to as Voice over LTE (VoLTE).VoLTE is specified, for example, in Permanent Reference Document (PRD)IR.92 of the GSM Association (GSMA), entitled “IMS Profile for Voice andSMS,” version 7.0, Mar. 3, 2013, which is incorporated herein byreference.

SUMMARY OF THE INVENTION

An embodiment of the present invention that is described herein providesa method for communication, including monitoring communication trafficin a wireless data network that serves wireless communication terminals.Control messages, relating to setting-up of voice calls over thewireless data network for the wireless communication terminals, areidentified in the communication traffic. Precedence is given to theidentified control messages, relative to other communication trafficthat is not related to setting-up of voice calls. The communicationtraffic is controlled selectively in accordance with the precedence.

In some embodiments, the wireless data network includes a Long-TermEvolution (LTE) or LTE-Advanced (LTE-A) network, and the voice callsinclude Voice-over-LTE (VoLTE) calls. In some embodiments, monitoringthe communication traffic is performed on a backhaul interface betweenbase stations and network elements of the wireless data network. In anembodiment, the wireless data network includes a Long-Term Evolution(LTE) or LTE-Advanced (LTE-A) network, and the backhaul interfaceincludes an S1 interface.

In another embodiment, monitoring the communication traffic includesbuffering the communication traffic in one or more queues, andselectively controlling the communication traffic includes delaying thebuffered traffic that is not related to setting-up of voice calls.

In yet another embodiment, identifying the control messages includesintercepting a message that is sent from a wireless communicationterminal to a network element of the wireless data network and relatesto setting up a voice call for the wireless communication terminal, andthe method includes sending to the wireless communication terminal aresponse to the message, before the network element responds to themessage.

In still another embodiment, identifying the control messages includesintercepting a message that is sent from a network element of thewireless data network to a wireless communication terminal and relatesto setting up a voice call for the wireless communication terminal, andthe method includes sending to the network element a response to themessage, before the wireless communication terminal responds to themessage.

There is additionally provided, in accordance with an embodiment of thepresent invention, a communication apparatus including an interface andprocessing circuitry. The interface is configured for connecting to awireless data network that serves wireless communication terminals. Theprocessing circuitry is configured to monitor communication traffic inthe wireless data network, to identify in the communication trafficcontrol messages relating to setting-up of voice calls over the wirelessdata network for the wireless communication terminals, to giveprecedence to the identified control messages relative to othercommunication traffic that is not related to setting-up of voice calls,and to selectively control the communication traffic in accordance withthe precedence.

There is further provided, in accordance with an embodiment of thepresent invention, a method for communication including, in a wirelessdata network, monitoring communication conditions at an intermediatelocation between a wireless communication terminal and a network elementthat provides voice-call services over the wireless data network to thewireless communication terminal. Upon detecting that the communicationconditions are expected to cause the wireless communication terminal tosend a notification to the network element, an early notification issent to the network element on behalf of the wireless communicationterminal.

In some embodiments, detecting the communication conditions and sendingthe early notification are performed during a voice call conducted bythe wireless communication terminal. In an embodiment, sending the earlynotification is performed independently of and transparently to thewireless communication terminal.

In a disclosed embodiment, detecting the communication conditions isperformed at a point in time at which the wireless communicationterminal is unaware that the communication conditions warrant sendingthe notification. In an embodiment, the wireless data network includes aLong-Term Evolution (LTE) or LTE-Advanced (LTE-A) network, and thevoice-call services include Voice-over-LTE (VoLTE) services. In anexample embodiment, the intermediate location includes a backhaulinterface of the wireless data network.

There is also provided, in accordance with an embodiment of the presentinvention, a communication apparatus including an interface andprocessing circuitry. The interface is configured for connecting to awireless data network that serves wireless communication terminals Theprocessing circuitry is configured to monitor communication conditionsat an intermediate location between a wireless communication terminaland a network element that provides voice-call services over thewireless data network to the wireless communication terminal, and, upondetecting that the communication conditions are expected to cause thewireless communication terminal to send a notification to the networkelement, to send an early notification to the network element on behalfof the wireless communication terminal.

There is additionally provided, in accordance with an embodiment of thepresent invention, a method for communication including, in a wirelessdata network in which a network element provides voice-call services towireless communication terminals, detecting a notification in which awireless communication terminal notifies the network element of degradedreception performance. A modification, which the network element isexpected to perform in a transmission characteristic to the wirelesscommunication terminal in response to the notification, is predicted.In-flight communication traffic, which is en-route to the wirelesscommunication terminal and whose transmission characteristic is not yetmodified in response to the notification, is intercepted. The predictedmodification is applied to the in-flight communication traffic.

In some embodiments, predicting and applying the modification areperformed during a voice call conducted by the wireless communicationterminal. In an embodiment, predicting and applying the modification areperformed independently of and transparently to the network element.

In a disclosed embodiment, applying the modification includes modifyinga speech coding scheme used in a voice call conducted by the wirelesscommunication terminal. Additionally or alternatively, applying themodification includes modifying an error correction coding scheme usedin a voice call conducted by the wireless communication terminal.

In some embodiments, the wireless data network includes a Long-TermEvolution (LTE) or LTE-Advanced (LTE-A) network, and the voice-callservices include Voice-over-LTE (VoLTE) services. In an embodiment,detecting the notification and applying the modification are performedon a backhaul interface of the wireless data network.

There is further provided, in accordance with an embodiment of thepresent invention, a communication apparatus including an interface andprocessing circuitry. The interface is configured for connecting to awireless data network in which a network element provides voice-callservices to wireless communication terminals. The processing circuitryis configured to detect a notification in which a wireless communicationterminal notifies the network element of degraded reception performance,to predict a modification that the network element is expected toperform in a transmission characteristic to the wireless communicationterminal in response to the notification, to intercept in-flightcommunication traffic that is en-route to the wireless communicationterminal and whose transmission characteristic is not yet modified inresponse to the notification, and to apply the predicted modification tothe in-flight communication traffic.

The present invention will be more fully understood from the followingdetailed description of the embodiments thereof, taken together with thedrawings in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram that schematically illustrates a LTEcommunication network employing VoLTE enhancement, in accordance with anembodiment of the present invention;

FIG. 2 is a flow chart that schematically illustrates a method forreducing the latency of VoLTE call setup, in accordance with anembodiment of the present invention;

FIG. 3 is a flow chart that schematically illustrates a method forenhancing VoLTE calls using RTCP proxy operations, in accordance with anembodiment of the present invention; and

FIG. 4 is a flow chart that schematically illustrates a method forenhancing VoLTE calls using IMS proxy operations, in accordance with anembodiment of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS Overview

Embodiments of the present invention that are described herein providemethods and systems for improving the performance of setting-up andconducting voice calls over wireless data networks. The embodimentsdescribed herein refer mainly to VoLTE calls conducted over LTE andLTE-A networks, but the disclosed techniques can be used with othersuitable types of voice calls and data networks.

In some embodiments, a VoLTE enhancement system is deployed at asuitable intermediate location in an LTE or LTE-A network, between thewireless communication terminals and the IP Multimedia Subsystem (IMS)that provides the VoLTE service. In the embodiments described herein,the system is coupled to the S1 backhaul interface of the network. Thisintermediate location enables the system to enhance VoLTE performance invarious ways, e.g., to buffer and forward VoLTE traffic selectively, topredict detrimental communication conditions and react to them quickly,and/or to act as a proxy for the wireless terminals and/or the IMS.

In some embodiments, the system buffers the communication traffic on theS1 interface, identifies traffic related to setting-up of VoLTE calls,and gives this traffic precedence over other traffic. This schemereduces the setup time of VoLTE calls, especially when call setuptraffic contends for resources with other traffic.

In other embodiments, the system intercepts notifications in whichwireless communication terminals inform the IMS of reception problems.Upon detecting such a notification, the system modifies the VoLTE calldata in-flight between the IMS and the terminal, before the IMS reactsto the notification. For example, the system may modify the speechcoding scheme or error correction coding scheme before the IMS performsthis change. This proxy operation shortens the reaction time to changesin communication conditions.

In yet other embodiments, the system monitors the communicationconditions at its intermediate location in the network. By virtue of itslocation, the system is able to detect detrimental communicationconditions long before the wireless communication terminals are able todo so. Upon detecting that the communication conditions are expected tocause a wireless communication terminal to send a notification to theIMS, the system sends the IMS an early notification on behalf of theterminal. As with the previous technique, this proxy operation speeds-upthe response to changes in communication conditions.

The methods and systems described herein overcome two of the majorchallenges of VoLTE-Long call setup times and long response time tochanges in communication conditions. As such, the disclosed techniquesimprove VoLTE performance and quality, and enhance VoLTE userexperience.

System Description

FIG. 1 is a block diagram that schematically illustrates a VoLTEenhancement system 20 deployed in an LTE or LTE-A communication network24, in accordance with an embodiment of the present invention. System 20is used for improving the performance of setting up and conducting VoLTEvoice calls, using methods that are described herein.

FIG. 1 shows a simplified view of an LTE or LTE-A network, focusing onthe major network elements and interfaces that are of relevance to thedisclosed techniques. In this example, wireless terminals referred to asUser Equipment (UE) 28, communicate over wireless channels with basestations referred to as eNodeB 32. The figure shows a single UE 28 and asingle eNodeB 32 for the sake of clarity, but real-life networkstypically comprise multiple UE and multiple eNodeBs.

The network-side of network 24 comprises one or more Serving Gateways(S-GW) 36, a Mobility Management Entity (MME) 40, one or more Packetdata network Gateways (P-GW) 44, and an IP Multimedia Subsystem (IMS)48. The interface that connects eNodeBs 32 with S-GW 36 and MME isdenoted S1, and comprises an S1-U interface (between the eNodeBs and theS-GW) and an S1-AP interface (between the eNodeBs and the MME). The S1interface (including both S1-U and S1-AP is sometimes referred to asbackhaul). The interface between the MME and S-GW is denoted S11, andthe interface between the S-GW and P-GW is denoted S5/8.

The network elements and interfaces depicted in FIG. 1 are specified,for example, in a 3GPP specification entitled “Technical SpecificationGroup Services and System Aspects; General Packet Radio Service (GPRS)enhancements for Evolved Universal Terrestrial Radio Access Network(E-UTRAN) access (Release 13),” TS 23.401, version 13.2.0, March, 2015;and in an ETSI specification entitled “LTE; Evolved UniversalTerrestrial Radio Access (E-UTRA) and Evolved Universal TerrestrialRadio Access Network (E-UTRAN); Overall description; Stage 2,” (3GPP TS36.300, version 8.9.0 Release 8), July, 2007, which are incorporatedherein by reference.

In order to set up VoLTE calls over network 24, UE should communicatewith IMS 48, which provides the VoLTE service. The UE is assumed to bein a connected state, i.e., the network is aware of the UE existence andallows it to transact. Typically, UE 28 and MME 40 create a logicalconnection (referred to as a “bearer”) between UE 28 and IMS 48, byexchanging control messages on the S1 interface.

The bearer connecting UE 28 and IMS 48 is an end-to-end connection, viaeNodeB 32, S-GW 36 and P-GW 44. The bearer thus spans both the S1 ands5/8 interfaces. The exchange of messages that sets up the bearer alsoinvolves some communication between MME 40 and S-GW 36 on the S11interface, and between MME 40 and P-GW 44 on the S11 and S5/8interfaces. Once set up, a Session Initiation Protocol (SIP) connectionis carried over this bearer. The SIP connection allows the UE and IMS tointeract and take various actions, e.g., creating a voice session. Thefirst bearer is thus also referred to herein as a “SIP bearer.”

Creating a voice session or setting up a VoLTE phone call typicallyinvolves setting up a second bearer between UE 28 and IMS 48. The secondbearer is created for carrying the call content itself (as opposed tothe first bearer that is used for signaling and control). To set up thesecond bearer, control messages are again exchanged between UE 28, MME40, S-GW 36 and P-GW 44. Once the second bearer is set up, the call maybe conducted.

A VoLTE call is typically carried over Real-Time Transport Protocol(RTP). In parallel, RTP Control Protocol (RTCP) is typically used tomonitor transmission statistics and Quality-of-Service (QoS) of thecall. RTP and RTCP are specified, for example, in Request For Comments(RFC) 3350 of the Internet Engineering Task Force (IETF), entitled “RTP:A Transport Protocol for Real-Time Applications,” July, 2003, which isincorporated herein by reference. Both RTP and RTCP messages are carriedover the second bearer that carries the call. The second bearer is thusalso referred herein to as a “RTP bearer.”

As can be appreciated from the description above, setting up andconducting VoLTE calls involves complex and signaling-intensiveprocesses. In practice, these processes are often long and slow to reactto changes in network conditions, and may therefore cause poor qualityand user experience.

Thus, in some embodiments, network 24 deploys a VoLTE enhancement system20 that enhances the quality and performance of VoLTE calls. Severalenhancement schemes are described in details below. In the presentexample, system 20 is located on the S1 interface, and comprises aninterface 50 for connecting to the S1 interface, and a processor 52 thatis configured to carry out the methods described herein. System 20 maybe positioned at any suitable position on the S1 interface, e.g.,adjacent to eNodeB 32 or adjacent to MME 40 or S-GW 36. Generally,however, system 20 should have access to both the S1-U and S1-APinterfaces.

The configurations of system 20 and network 24 in FIG. 1 are exampleconfigurations, which is chosen purely for the sake of conceptualclarity. In alternative embodiments, any other suitable configurationscan be used. For example, in the embodiments described herein system 20is coupled to the S1 interface. In alternative embodiments, however,system 20 may be deployed at other suitable intermediate locations innetwork 24, between IMS 48 and UEs 28. As another example, although theembodiments described herein refer mainly to LTE/LTE-A networks and toVoLTE voice calls, the disclosed techniques can be used for enhancingthe performance of other suitable types of voice calls over othersuitable wireless data networks.

The different elements of system 20 may be implemented using anysuitable hardware, such as in an Application-Specific Integrated Circuit(ASIC) or Field-Programmable Gate Array (FPGA). In some embodiments,some elements of system 20 can be implemented using software, or using acombination of hardware and software elements. Generally, the functionsof processor 52 described herein can be carried out using any suitableprocessing circuitry, in hardware and/or software.

In some embodiments, processor 52 comprises a general-purpose processor,which is programmed in software to carry out the functions describedherein. The software may be downloaded to the computer in electronicform, over a network, for example, or it may, alternatively oradditionally, be provided and/or stored on non-transitory tangiblemedia, such as magnetic, optical, or electronic memory.

Reducing the Latency of Voice-Over-LTE Call Setup

One major drawback of the VoLTE call setup process described above isthe long call setup time it may incur. The call setup time may beparticularly long if the SIP connection and the SIP bearer carrying itdo not exist and need to be set up. This scenario occurs, for example,when the UE was not engaged in a VoLTE call for a long time. In such acase, the SIP bearer would typically be released in order to free UE andnetwork resources. In such a scenario, both the SIP bearer and the RTPbearer have to be set up before the call can start. The resulting callsetup time, as experienced by the used, may be on the order of tens tohundreds of milliseconds typically, and in extreme cases up to severalseconds.

In some embodiments, VoLTE enhancement system 20 reduces the setup timeof VoLTE calls by giving precedence to traffic relating to VoLTE callsetup over other traffic. This prioritization mechanism reduces delaysthat are caused by resource contention on the S1 interface, and possiblyby resource contention in the eNodeB or UE.

As noted above, system 20 may be positioned at any suitable position onthe S1 interface, e.g., adjacent to eNodeB 32 or adjacent to MME 40 orS-GW 36, as long as the system has access to both the S1-U and S1-APinterfaces. In some embodiments, processor 52 of system 20 can estimatethe traffic volume (e.g., number of packets) that is queued in eNodeB32, and/or at other points along the S1 interface. This information canbe used, for example, to recognize that congestion is building up.

FIG. 2 is a flow chart that schematically illustrates a method forreducing the latency of VoLTE call setup, in accordance with anembodiment of the present invention. The method begins with processor 52of system 20 buffering the communication traffic that traverses the S1interface, at a buffering step 60. Processor 52 typically buffers all S1traffic, including both inbound and outbound traffic, and including thetraffic on the S1-U interface and the traffic on the S1-AP interface.Buffering may be carried out using any suitable memory configuration,e.g., in one or more queues.

At a traffic classification step 64, processor 52 checks which of thebuffered traffic is related to setup of VoLTE calls. In variousembodiments, processor 52 may check, for example, for messages thatrelate to setting up of the SIP bearer and RTP bearer described above.

For a given portion of the traffic, e.g., packet, flow or transaction,if the traffic is found to be unrelated to VoLTE call setup, processor52 suppresses (i.e., throttles-down) the traffic before forwarding itonwards, at a suppressed forwarding step 68. If, on the other hand, thetraffic is found to be related to VoLTE call setup, processor 52forwards the traffic onwards without suppression, at a direct forwardingstep 72.

Processor 52 may suppress the traffic unrelated to VoLTE call setup invarious ways. In one example embodiment, processor 52 delays thistraffic, i.e., holds it in the queues for a longer period of time,relative to the traffic related to VoLTE call setup. In anotherembodiment, processor 52 buffers the traffic related to VoLTE call setupand the traffic unrelated to VoLTE call setup in different queues,forwards traffic from the former queue with high priority, and forwardstraffic from the latter queue only when the former queue is empty. In atypical embodiment, processor 52 suppresses the traffic unrelated toVoLTE call setup only if and when necessary, not necessarily always.When conditions permit, suppression is not performed.

The examples above are depicted purely for the sake of conceptualclarity. In alternative embodiments, processor 52 may use any othersuitable scheme of buffering and selectively forwarding traffic, inorder to give precedence to VoLTE call setup traffic over other traffic.

In some embodiments, processor 52 may shorten the VoLTE call setup timeby functioning as a proxy for UE 28 and/or for IMS 48. For example,processor 52 may intercept a message that is sent from UE 28 to IMS 48and relates to setting up a VoLTE call for the UE. Such a message mayrelate, for example, to setting up of the SIP or RTP bearer for thecall. When identifying such a message, processor 52 may send an earlyacknowledgement or other suitable response to the UE, before the IMSresponds. Processor 52 may intercept and discard the genuine responsearriving from the IMS, in order to avoid duplicate responses.

A similar process may be carried out in the opposite direction:Processor 52 may intercept a message that is sent from IMS 48 to UE 28and relates to setting up a VoLTE call for the UE. Such a message mayrelate, for example, to setting up of the SIP or RTP bearer for thecall. When identifying such a message, processor 52 may send an earlyacknowledgement or other suitable response to the IMS, before the UEresponds. Processor 52 may intercept and discard the genuine responsearriving from the UE, in order to avoid duplicate responses.

Enhancing Voice-Over-LTE Calls Using RTCP Proxy Operation

Another drawback of the long latencies encountered in VoLTEcommunication is the long reaction time to changes in communicationconditions or other events. Consider, for example, a scenario in whichUE 28 identifies a degradation in reception quality during a VoLTE call.The UE typically notifies IMS 48 of the problem using RTCP signalingover the RTP bearer described above. The notification traverses thenetwork and reaches the IMS. The IMS may react to the notification byadapting one or more transmission characteristics, e.g., switching to amore robust speech coding scheme (codec) or Error Correction Coding(ECC) scheme.

In order for the reception problem to be resolved, a full round-tripfeedback loop has to be completed. The UE has to detect the problem andnotify the IMS; The IMS needs to react; the data after reaction has toreach the UE; the UE has to signal to the IMS that the problem has beenresolved, and finally the IMS has to terminate the adaptation process.During this entire process, which may well take an order of a second tocomplete, the quality of the VoLTE call may suffer severe degradation.

In some embodiments, VoLTE enhancement system 20 reduces the reactiontime illustrated above, by sending early notifications to IMS 48 onbehalf of UE 28. As a result, the duration of degraded receptionexperienced by the UE is shortened significantly. In some embodiments,processor 52 of system 20 anticipates scenarios in which UE 28 is likelyto send an RTCP notification that notifies IMS 48 of a receptionproblem. Because of its intermediate location in network 24 processor 52is often able to predict such scenarios long before the UE senses anyreception degradation. As noted above, the entire round-trip time forconventionally detecting and resolving the problem is long.

Processor 52 may perform this prediction, for example, by sensing thatresources in eNodeB 32 or otherwise on the backhaul interface areheavily loaded or overloaded. Such a condition is often a good predictorthat packets will soon be dropped. Processor 52 may detect suchconditions, for example, by monitoring control traffic or user data overthe S1 interface, information relating to handovers, or any othersuitable information. Generally, processor 52 may detect any suitablecommunication conditions for this purpose.

Upon detecting network conditions that are expected to cause UE 28 tosend an RTCP notification to IMS 48, processor 52 generates and sends anearly notification on the UE's behalf. The UE is typically unaware ofthe existence of the early notification. The early notificationtypically has the same format as the genuine notification that the UE isexpected to send.

The IMS is typically unaware that the early notification did notoriginate from the UE but from an intermediate party. The IMS thusresponds to the early notification in the same manner it would haveresponded to the genuine notification from the UE. For example, the IMSmay switch to a more robust speech coding scheme (codec) or ErrorCorrection Coding (ECC) scheme for subsequent communication with thisUE.

Since the IMS responds to the early notification (sent from system 20)and not to the genuine notification (sent from UE 28), the overallresponse time is shortened considerably. In an embodiment, processor 52may intercept and discard the genuine notification arriving from the UE,in order to avoid duplicate notifications. In some cases processor 52may modify the genuine notification arriving from the UE, such asre-stamping message sequence numbers if needed.

FIG. 3 is a flow chart that schematically illustrates a method forenhancing VoLTE calls using RTCP proxy operations, in accordance with anembodiment of the present invention. The method begins with processor 52of system 20 estimating the communication conditions, at a conditionassessment step 80. Processor 52 checks whether the estimatedcommunication conditions are expected to cause UE 28 to send an RTCPnotification to IMS 48, at a condition checking step 84. If so,processor 52 sends IMS 48 an early RTCP notification on behalf of (butindependently of) UE 28, at an early notification step 88.

Enhancing Voice-Over-LTE Calls Using IMS Proxy Operation

In some embodiments, VoLTE enhancement system 20 reduces theabove-described round-trip reaction time by acting as a proxy to IMS 48.Consider an example scenario in which UE 28 encounters a receptionproblem during a VoLTE call, and therefore sends to IMS 48 an RTCPnotification that reports the problem. Typically, IMS 48 would react tothe notification by modifying some characteristic of subsequent VoLTEcall traffic to this UE, such as switching to a more robust speechcoding scheme (codec) or Error Correction Coding (ECC) scheme.

In order to shorten the reaction time in such scenarios, processor 52 ofsystem 20 detects the RTCP notification sent by UE 28, and predicts themodification that the IMS is likely to perform to the characteristics ofsubsequent VoLTE call traffic. Processor 52 then intercepts in-flightVoLTE call traffic destined to the UE, and modifies the trafficaccordingly.

Assume, for example, that processor 52 predicts that the IMS is likelyto switch from a first speech coding scheme to a second speech codingscheme in response to the RTCP notification. In such a scenario,processor 52 may intercept VoLTE call traffic that is in-flight, i.e.,that was transmitted en-route to the UE before the modification tookeffect and is still coded with the first speech coding scheme.

Upon intercepting such traffic, processor 52 changes the speech codingin the traffic from the first scheme to the second scheme, and forwardsthe modified traffic toward the UE. As a result, the reaction time tothe RTCP request, as seen by the UE, is considerably shorter than thefull round-trip delay.

The example above refers to modification of speech coding scheme, butthe disclosed technique can be applied in a similar manner to othercharacteristics, such as ECC. Typically, the modification applied byprocessor 52 is performed independently of the actions of IMS 48,without coordination with the IMS and transparently to the IMS. In someembodiments, processor 52 continues to monitor the RTCP traffic, forexample in order to verify whether its prediction was correct and tomake additional changes if needed.

FIG. 4 is a flow chart that schematically illustrates a method forenhancing VoLTE calls using IMS proxy operations, in accordance with anembodiment of the present invention. The method begins with processor 52of system 20 intercepting an RTCP notification sent from UE 28 to IMS 48on the S1 interface, at a notification detection step 90. At amodification step 94, processor modifies one or more characteristics ofin-flight VoLTE call traffic destined to the UE, using the modificationthat the IMS is predicted to perform.

Although the embodiments described herein mainly address Voice over LTE,the methods and systems described herein can also be used in otherapplications, such as in various Voice over IP (VoIP) and mediastreaming applications.

It will thus be appreciated that the embodiments described above arecited by way of example, and that the present invention is not limitedto what has been particularly shown and described hereinabove. Rather,the scope of the present invention includes both combinations andsub-combinations of the various features described hereinabove, as wellas variations and modifications thereof which would occur to personsskilled in the art upon reading the foregoing description and which arenot disclosed in the prior art. Documents incorporated by reference inthe present patent application are to be considered an integral part ofthe application except that to the extent any terms are defined in theseincorporated documents in a manner that conflicts with the definitionsmade explicitly or implicitly in the present specification, only thedefinitions in the present specification should be considered.

The invention claimed is:
 1. A method for communication, comprising: ina wireless data network, monitoring communication conditions at anintermediate location between a wireless communication terminal and anetwork element that provides voice-call services over the wireless datanetwork to the wireless communication terminal; upon detecting, at theintermediate location, that the communication conditions are expected tocause the wireless communication terminal to send a notification ondegrading reception quality of a voice call to the network element,sending, from the intermediate location, an early notification ondegrading reception quality of a voice call, in a format as if thenotification originated from the wireless communication terminal, to thenetwork element on behalf of the wireless communication terminal; anddetecting, at the intermediate location, a notification transmitted fromthe wireless terminal to the network element, similar to the earlynotification, and discarding the detected notification.
 2. The methodaccording to claim 1, wherein detecting the communication conditions andsending the early notification are performed during a voice callconducted by the wireless communication terminal.
 3. The methodaccording to claim 1, wherein sending the early notification isperformed independently of and transparently to the wirelesscommunication terminal.
 4. The method according to claim 1, whereindetecting the communication conditions is performed at a point in timeat which the wireless communication terminal is unaware that thecommunication conditions warrant sending the notification.
 5. The methodaccording to claim 1, wherein the wireless data network comprises aLong-Term Evolution (LTE) or LTE-Advanced (LTE-A) network, and whereinthe voice-call services comprise Voice-over-LTE (VoLTE) services.
 6. Themethod according to claim 1, wherein the intermediate location comprisesa backhaul interface of the wireless data network.
 7. The methodaccording to claim 1, wherein the early notification on degradingreception quality of a voice call comprises a notification configured tocause the network element to change a speech coding scheme of the voicecall.
 8. The method according to claim 1, wherein the early notificationon degrading reception quality of a voice call comprises a notificationconfigured to cause the network element to change an error correctioncoding scheme of the voice call.
 9. The method according to claim 1,wherein detecting that the communication conditions are expected tocause the wireless communication terminal to send a notification ondegrading reception quality comprises detecting that a network node isheavily loaded or overloaded.
 10. A communication apparatus, comprising:an interface for connecting to a wireless data network that serveswireless communication terminals; and processing circuitry, which isconfigured to monitor communication conditions at an intermediatelocation between a wireless communication terminal and a network elementthat provides voice-call services over the wireless data network to thewireless communication terminal, and, upon detecting that thecommunication conditions are expected to cause the wirelesscommunication terminal to send a notification on degrading receptionquality of a voice call to the network element, to send an earlynotification on degrading reception quality of a voice call, in a formatas if the notification originated from the wireless communicationterminal, to the network element on behalf of the wireless communicationterminal, and upon detecting, at the intermediate location, anotification transmitted from the wireless terminal to the networkelement, similar to the early notification, to discard the detectednotification.
 11. The apparatus according to claim 10, wherein theprocessing circuitry is configured to detect the communicationconditions and send the early notification during a voice call conductedby the wireless communication terminal.
 12. The apparatus according toclaim 10, wherein the processing circuitry is configured to send theearly notification independently of and transparently to the wirelesscommunication terminal.
 13. The apparatus according to claim 10, whereinthe wireless data network comprises a Long-Term Evolution (LTE) orLTE-Advanced (LTE-A) network, and wherein the voice-call servicescomprise Voice-over-LTE (VoLTE) services.
 14. The apparatus according toclaim 10, wherein the intermediate location comprises a backhaulinterface of the wireless data network.
 15. A method for communication,comprising: in a wireless data network in which a network elementprovides voice-call services to wireless communication terminals,detecting, by an enhancement system at an intermediate location betweenthe wireless communication terminals and the network element, anotification in which a wireless communication terminal notifies thenetwork element of degraded reception performance; predicting, by theenhancement system, a modification that the network element is expectedto perform in a transmission characteristic to the wirelesscommunication terminal in response to the notification; andintercepting, by the enhancement system, in-flight communication trafficthat is en-route to the wireless communication terminal and whosetransmission characteristic is not yet modified in response to thenotification, and applying the predicted modification to the in-flightcommunication traffic.
 16. The method according to claim 15, whereinpredicting and applying the modification are performed during a voicecall conducted by the wireless communication terminal.
 17. The methodaccording to claim 15, wherein predicting and applying the modificationare performed independently of and transparently to the network element.18. The method according to claim 15, wherein applying the modificationcomprises modifying a speech coding scheme used in a voice callconducted by the wireless communication terminal.
 19. The methodaccording to claim 15, wherein applying the modification comprisesmodifying an error correction coding scheme used in a voice callconducted by the wireless communication terminal.
 20. The methodaccording to claim 15, wherein the wireless data network comprises aLong-Term Evolution (LTE) or LTE-Advanced (LTE-A) network, and whereinthe voice-call services comprise Voice-over-LTE (VoLTE) services. 21.The method according to claim 15, wherein detecting the notification andapplying the modification are performed on a backhaul interface of thewireless data network.
 22. A communication apparatus, comprising: aninterface for connecting to a wireless data network in which a networkelement provides voice-call services to wireless communicationterminals, at an intermediate location between the wirelesscommunication terminals and the network element; and processingcircuitry, which is configured to detect in signals collected throughthe interface at the intermediate location, a notification in which awireless communication terminal notifies the network element of degradedreception performance, to predict a modification that the networkelement is expected to perform in a transmission characteristic to thewireless communication terminal in response to the notification, tointercept in-flight communication traffic that is en-route to thewireless communication terminal and whose transmission characteristic isnot yet modified in response to the notification, and to apply thepredicted modification to the in-flight communication traffic.
 23. Theapparatus according to claim 22, wherein the processing circuitry isconfigured to predict and apply the modification during a voice callconducted by the wireless communication terminal.
 24. The apparatusaccording to claim 22, wherein the processing circuitry is configured topredict and apply the modification independently of and transparently tothe network element.
 25. The apparatus according to claim 22, whereinthe processing circuitry is configured to apply the modification bymodifying a speech coding scheme used in a voice call conducted by thewireless communication terminal.
 26. The apparatus according to claim22, wherein the processing circuitry is configured to apply themodification by modifying an error correction coding scheme used in avoice call conducted by the wireless communication terminal.
 27. Theapparatus according to claim 22, wherein the wireless data networkcomprises a Long-Term Evolution (LTE) or LTE-Advanced (LTE-A) network,and wherein the voice-call services comprise Voice-over-LTE (VoLTE)services.
 28. The apparatus according to claim 22, wherein theprocessing circuitry is configured to detect the notification and applythe modification on a backhaul interface of the wireless data network.